Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
  • H10K59/80—Constructional details
  • H10K59/84—Parallel electrical configurations of multiple OLEDs
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
  • H05B45/40—Details of LED load circuits
  • H05B45/42—Antiparallel configurations
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/80—Constructional details
  • H10K50/805—Electrodes
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
  • H10K71/841—Applying alternating current [AC] during manufacturing or treatment

Definitions

• Light emitting device adapted for AC drive
• the present invention relates to a light emitting device with a plurality of light emitted elements adapted for AC drive, and a luminaire comprising such a light emitting device.
• LEDs light-emitting-diodes
• Spectacular progress in the brightness, lumen efficacy and affordability of solid state light sources enables new lighting applications that are no longer restricted to niche markets.
• LEDs offer several advantages over traditional light sources, such as long lifetime, superior efficiency, low operating voltage, design flexibility, more pure spectral colors, fast response times.
• LEDs are becoming more and more suited for making illumination devices, like color variable luminaires, spotlights, LCD backlighting, architectural lighting, stage lighting, etc.
• solid state light sources such as organic LEDs (OLEDs)
• OLEDs organic LEDs
• Brightness can be controlled with Amplitude Modulation (AM) or with Pulse Width Modulation (PWM) where the LED is duty-cycled. Often PWM is applied for low losses in the driver, and allowing freedom of system supply voltage.
• AM Amplitude Modulation
• PWM Pulse Width Modulation
• light emitting devices covering a larger surface are required. Many LEDs are then connected in parallel on a substrate, or, in case of OLED, one or several OLED tiles covering a large surface are formed.
• OLED organic light emitting diode
• the occurrence of short circuits become a problem, as the entire system is short circuited and no light is emitted in case of a large short-circuit current. The current also results in unwanted power dissipation and heat generation.
• US patent 7,052,473 proposes AC drive of LEDs, with two LEDs connected anti-parallel in series with a capacitor. During every current cycle, a limited amount of charge is forced through the LED resulting in a light flash. This charge is stored on the capacitor, which stops the current. The charge is available for the next cycle to be used again.
• the anti- parallel diode ensures back-flow of the charge. In this case full double-phase operation is assured.
• a light emitting device comprising a first common electrode, a structured conducting layer, forming a set of electrode pads electrically isolated from each other, a dielectric layer, interposed between the first common electrode layer and the structured conducting layer, a second common electrode, and a plurality of light emitting elements.
• Each light emitting element is electrically connected between one of the electrode pads and the second common electrode, so as to be connected in series with a capacitor comprising one of the electrode pads, the dielectric layer, and the first common electrode.
• a thin film layer i.e. thickness in the order of micrometers
• the dielectric layer interposed between two conducting layers is used to create a capacitive coupling between the layers.
• One of the layers is then structured into pads, forming a plurality of independently connected capacitors.
• the light emitting elements are then connected between the pads and a common electrode, so that each light emitting element is connected in series with one of the capacitors.
• an alternating voltage is applied between the first and second common electrodes, the light emitting elements will be powered through a capacitive coupling, also providing current limitation.
• a shorts circuit failure in one light emitting element will affect only light emitting elements connected to the same capacitor. Further, the short circuit current will be limited by this capacitor.
• the capacitors are charged/discharged every cycle, so no loss of charge occurs and power dissipation is small. Any short-peak currents will introduce small resistive power- loss I 2 R across the resistance in the conductive layer.
• each capacitor is determined by the thickness of the dielectric layer, its permittivity, and the area of each pad electrode.
• the current through each circuit will be determined by this capacitance, the applied voltage, and the frequency.
• a suitable frequency in the order of kHz can be obtained.
• one or several of the light emitting elements may be connected to more than one pad, each such electrode pad forming part of a separate capacitor. Such a design may provide economical advantages.
• the second common electrode can comprise an electrode mesh surrounding the electrode pads.
• each electrode pad can be adjacent to the electrode mesh.
• each pad or groups of pads may be surrounded by the mesh. This allows connection of the light emitting elements in places where the pad is adjacent to the mesh, thus avoiding long connection wires or tracks. By keeping the connection wires or tracks short, the chances are increased that a specific light emitting element will be active when the device is cut to measure.
• the light emitting elements may be light emitting diodes, including semi- conducting LEDs, small-molecule organic LEDs and polymer organic LEDs.
• the plurality of LEDs may include a first group having a cathode connected to one of the pads, and a second group having an anode connected to one of the pads.
• Each pad can be connected to a pair of anti-parallel connected LEDs, where the pair includes one LED from the first group and one LED from the second group. This will ensure that the alternating current through each capacitor is used efficiently to activate the various LEDs.
• a device according to the present invention allows the presence of short circuits in the light emitting elements. The associated short-circuit current and loss of light will be restricted to one section of light emitting elements. This is particularly advantageous when the light emitting elements are such that their light emitting characteristics depend on the current through the device, such as light emitting diodes.
• a device according to the present invention is thus suitable for any light emitting device with a plurality of LEDs that are driven by a common power (voltage) source.
• the carrier formed by the first common electrode, dielectric layer and pads can act as a substrate, on which organic layers, forming the OLEDs, are deposited.
• the organic layers must be aligned with the pads, so that one OLED is formed on top of each pad.
• the polarity of the OLEDs must be alternatingly arranged.
• the entire light emitting device has a layered structure, Further, in numerous occasions it is desirable that an illumination device is cut to measure i.e. its size and shape can easily be altered, so it will fit in any room and it can serve many purposes.
• the carrier composed of the common electrode layer, the structured electrode layer and the dielectric layer formed by materials suitable for being cut, e.g. by forming the various layers of suitable materials and thickness.
• the entire carrier, comprising the conductive layers and intermediate dielectric, may be cut to measure to any shape and size, even letters and figures, without destroying the capacitive coupling.
• a light emitting device may be combined with a small low voltage power supply to form a product which can find its way in numerous markets, such as signage, indoor architects, schools, wearable electronics and photonic textiles. If deemed advantageous, in order to give the lamp a certain optical functionality, it can be equipped with specific optical components such as diffusers, lenses, collimators etc.
• the light emitting device may be particularly useful in a luminaire, i.e. a device intended to illuminate an object or a surrounding.
• Figure 1 shows a circuit diagram of a prior art LED array.
• Figure 2a-c shows various steps of manufacturing a light emitting device according to a first embodiment of the present invention.
• Figure 3 shows a circuit diagram of the device in figure 2c.
• Figure 4 shows schematic perspective view of a light emitting device according to a second embodiment of the present invention.
• Figure 1 shows a circuit diagram of a light emitting device adapted to AC drive, with a plurality of LEDs, connected according to US 7,052,473.
• Capacitors 1 are each connected in series with a pair of anti-parallel LEDs 2. It is apparent from figure 1 that any LED can be taken out of the matrix, without influencing the function of the other LEDs, apart from the single anti-parallel connected neighbor LED.
• each pair of LEDs requires its own pair of power wires, this is a difficult and expensive approach for a device with a large number of LEDs.
• a carrier 10 is formed by three layers: a first and a second conducting layer 11, 12 and an intermediate dielectric layer 13.
• the dielectric layer 13 can have the form of a thin - film layer with high permittivity.
• a carrier 10 of this kind may be manufactured using conventional techniques used for manufacturing circuit boards.
• the carrier 10 may obviously comprise additional layers in addition to these three layers, for example a structural support layer in a case where the carrier requires structural strength, or a protective cover layer if the carrier may be exposed to physical stress.
• the first conducting layer 11 forms a common electrode.
• the second conducting layer 12 is structured using a conventional technique such as etching.
• the layer is structured into a plurality of electrode pads 14, that are isolated from each other and from a surrounding electrode mesh 15.
• the pads are each completely surrounded by the mesh, but alternatively two or more pads are grouped adjacent to each other, and the entire group then surrounded by the mesh. However, it is advantageous if at least a portion of the edge of each pad extends along the mesh.
• a light emitting element 16 is connected between each pad and the mesh.
• the light emitting elements are light emitting diodes (LEDs), and a pair of LEDs 17a, 17b is connected in parallel between each electrode pad 14 and the mesh 15.
• One of the LEDs 17a is connected with its anode to the pad 14 and its cathode to the mesh 15, while the other LED 17b is connected with its cathode to the pad 14 and its anode to the mesh 15.
• Each LED pair 17a, 17b is thus connected in series with a capacitor 18 formed by one of the electrode pads 14, the dielectric layer 13, and the common electrode 11.
• each pad forms one terminal of a separate capacitor 18, having its other terminal in common with a plurality of other capacitors.
• each one of the LEDs will generate light during each half cycle of an alternating power source, and essentially all current will contribute to the generation of light.
• the capacitors will act as current limiters, and the carrier can be cut to measure without affecting the functionality.
• the resulting circuit diagram is depicted in figure 3. It is easy to realize that this circuit is functionally equivalent to the circuit in figure 1.
• the capacitance C will in turn depend on the area of each pad, the thickness of the dielectric layer, and the permittivity of the dielectric.
• each capacitor 18 and the driving frequency have to be matched with the available voltage, to obtain the required drive current.
• the desired value for the capacitance of each capacitor 18 will therefore be a trade-off between minimizing the short circuit current, and maximizing the light-output for a given supply voltage.
• a typical thickness in conventional circuit board manufacturing processes is 10-50 ⁇ m.
• ⁇ relative permittivity
• the capacitance will therefore be fairly low. For instance, assuming a typical drive voltage of around 10 V, a relatively high drive frequency, e.g.
• Such amplifiers have an extreme high electrical efficiency and are very cost efficient, so they are well suited to act as drivers for this cut to measure lamp.
• the light emitting elements 16 may be semi-conducting LEDs. Alternatively, they may be organic LEDs.
• FIG 4 A further embodiment of the present invention, especially suitable for OLED implementation is illustrated in figure 4, showing two anti-parallel OLEDs 20a, 20b.
• the illumination device 5' here again comprises first and second conductive layers 21, 22, and an intermediate dielectric layer 23.
• the second conductive layer 22 is here only divided into pads 24a, 24b, without any surrounding mesh. Instead, the pads 24a, 24b act as substrates, on which organic layers 26, 27 are deposited to form the OLEDs 20a, 20b.
• the organic layers typically comprise a hole- injection layer 26 (e.g. PEDOT) and a light emissive layer 27 (e.g. PPV).
• the organic layers 26, 27 are aligned with the pads, so that one OLED is formed on top of each pad.
• On top of the upper organic layer 27 of each OLED is deposited a final conducting layer to form a diode cathode 28a, 28b.
• the first conducting layer e.g. PEDOT
• Electrodes 21 is also structured, to form electrodes 25 that extend beneath one OLED in each pair of anti-parallel OLEDs.
• an electrode 25 may extend beneath a row of OLEDs.
• a first interconnecting element 29 is arranged to connect the pad 24a of the OLED located on top of the electrode 25 to the upper terminal 28b of the other OLED, and a second interconnecting element 30 is arranged to connect the upper terminal 28a of the OLED located on top of the electrode 25 to the pad 24b of the second OLED.
• a voltage source 32 is connected between the first conducting layer 21, which forms a first common electrode, and the interconnecting element 30, which forms a second common electrode.
• the dielectric layer 23 is structured, so as to extend underneath only one of the diodes. In this case the conducting layer 21 does not need to be structured into electrodes 25.
• both diodes are constructed simultaneously, according to the same layer deposition order, i.e. with layer 27 on top of layer 26.
• the organic layers 26 and 27 are deposited in reversed order on the pads 24a and 24b. This can be done by adequate technologies of material removal (etching, ablation etc) and material deposition (printing, spin-casting, evaporation etc). In this case, the interconnecting elements 29, 30 are not required. Further, neither the conducting layer 21 nor the dielectric layer 23 need to be structured.
• the number of capacitors should be chosen sufficiently large to allow for minimal loss of non- functional area. This will ensure that a failing section (OLEDs connected to one capacitor) is sufficiently small not to add too much short-circuit current and not to reduce too much the light-output. For instance, a given OLED tile with 100 expected shorts still operates at 90% of its maximum performance if the tile is divided in 1000 sections (which corresponds to 2000 'pixels').
• the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.
• the shape and arrangement of the electrode pads may be modified, as may the orientation and distribution of light emitting elements.
• the light emitting elements not necessarily are light emitting diodes.
• various light emitting elements may be suitable for use in a light emitting device according to the present invention.
• the present invention is applicable also to AC Electro Luminescence (EL) systems.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Electroluminescent Light Sources (AREA)
• Led Devices (AREA)
• Non-Portable Lighting Devices Or Systems Thereof (AREA)

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• 2009
  • 2009-06-11 CN CN2009801227429A patent/CN102067724B/zh active Active
  • 2009-06-11 RU RU2011101371/07A patent/RU2499331C2/ru active
  • 2009-06-11 US US12/995,483 patent/US8530906B2/en active Active
  • 2009-06-11 WO PCT/IB2009/052494 patent/WO2009153715A2/en active Application Filing
  • 2009-06-11 JP JP2011514168A patent/JP5670888B2/ja active Active
  • 2009-06-11 EP EP09766252.2A patent/EP2292077B1/en not_active Not-in-force
  • 2009-06-15 TW TW098119984A patent/TWI513358B/zh active

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